BUG Cleaner handling of querystring arguments when selecting locale

code/controller/TranslatableCMSMainExtension.php

@@ -40,7 +40,7 @@ class TranslatableCMSMainExtension extends Extension {
 					$req->param('Action'),
 					$req->param('ID'),
 					$req->param('OtherID'),
-					'?' . http_build_query($getVars)
+					($query = http_build_query($getVars)) ? "?$query" : null
 				));
 			}
 		}

javascript/CMSMain.Translatable.js

@@ -36,10 +36,19 @@
 				this._super();
 			},
 			onchange: function(e) {
-				var url = $.path.addSearchParams(
-					document.location.href.replace(/locale=[^&]*/, ''),
-					{locale: $(e.target).val()}
-				);
+				// Get new locale code
+				locale = {locale: $(e.target).val()};
+				
+				// Check existing url
+				search = /locale=[^&]*/;
+				url = document.location.href;
+				if(url.match(search)) {
+					// Replace locale code
+					url = url.replace(search, $.param(locale));
+				} else {
+					// Add locale code
+					url = $.path.addSearchParams(url, locale);
+				}
 				$('.cms-container').loadPanel(url);
 				return false;
 			}